JP3697750B2 - Secondary seal device for low temperature tank top piping and valve replacement method using the device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary seal device used when replacing a valve provided in a top pipe of a low-temperature tank that stores liquefied gas such as LNG and LPG, and a valve replacement method using the device.
[0002]
[Prior art]
A low-temperature tank that stores liquefied gas such as LNG and LPG is provided with a relatively large-diameter pipe (hereinafter referred to as a top pipe) as an injection pipe or a supply pipe on its roof or wall. A valve is attached to the tip.
Since this valve is the original valve of this low temperature tank, if the valve is inadvertently removed when replacing this valve, the liquefied gas will be ejected due to the pressure difference inside and outside the low temperature tank, making it impossible to work. . Therefore, when it was necessary to replace the valve, all the liquefied gas in the low temperature tank had to be removed. However, if the liquefied gas in the cryogenic tank is removed every time the valve is replaced, the operation of the plant or the like that receives the liquefied gas supply from the tank must be stopped for a long time, resulting in an economic loss. Very big.
[0003]
Therefore, when it is desired to replace the existing valve 5 such as a butterfly valve or a gate valve provided at the upper portion of the top pipe 2 of the low temperature tank 1 as shown in FIG. As shown in FIG. 16, a balloon made of a flexible member such as natural rubber (hereinafter referred to as a sealing balloon) is inflated to seal the top piping of the low-temperature tank and replace the valve. Hereinafter, a case where the butterfly valve 5 which is an existing valve is replaced with a gate valve 23 which is a new valve will be described in the order of steps with reference to the drawings.
(1) As a first step, in FIG. 11, a container 22 (hereinafter referred to as an air lock chamber) having a lower end opened is fixed to an upper portion of a butterfly valve 5 provided on an upper portion of the top pipe 2 of the low-temperature tank 1. . A seal balloon 4 is prepared in the air lock chamber 22, and an air supply tube 3 for sending air from the air supply device 26 to the seal balloon 4 is arranged in the axial direction of the top pipe 2 at the top of the air lock chamber 22. Are slidably provided. The air supply tube 3 and the air supply device 26 are connected via a valve 27. Further, when the butterfly valve 5 is opened, in order to prevent the inside of the air lock chamber 22 from becoming an explosive atmosphere, the inside of the air lock chamber 22 is nitrogenated by the nozzle 24 provided in the air lock chamber 22 from the nitrogen supply device 25. The air in the air lock chamber 22 is expelled from an openable / closable discharge hole (not shown) provided in the air lock chamber 22.
(2) As a second step, in FIG. 12, the butterfly valve 5 is opened and the sealing balloon 4 is inserted into the top pipe 2 through the gap, and the valve 27 is opened to supply air from the air supply device 26. Is supplied into the sealing balloon 4 and inflated, and pressed against the inner wall of the top pipe 2 for sealing.
(3) As a third step, in FIG. 13, the valve 27 is closed and the air supply tube 3 is removed from the air supply device 26, and then the air lock chamber 22 and the butterfly valve 5 are removed.
(4) As the fourth step, in FIG. 14, the gate valve 23 is attached to the top pipe 2, and the air lock chamber 22 is fixed to the top thereof, and purged with nitrogen as in (1).
(5) As a fifth step, in FIG. 15, the valve 27 is opened, the air in the sealing balloon 4 is extracted and deflated, the sealing balloon 4 is extracted from the gap of the gate valve 23, and then the gate valve 23 is closed.
(6) As a sixth step, in FIG. 16, the air lock chamber 22 is finally removed, and the replacement from the butterfly valve 5 (existing valve) to the gate valve 23 (new valve) is completed.
[0004]
Note that the liquefied gas in the low temperature tank 1 is a low temperature gas of −100 ° C. or lower. However, since there is no gas flow in the top pipe 2, it is normally kept at room temperature.
[0005]
[Problems to be solved by the invention]
However, in the above-described valve replacement method, the top pipe is sealed only with a sealing balloon. Therefore, if the sealing balloon is broken or deflated for some reason, liquefied gas is ejected and the work can be performed. It will disappear.
[0006]
The present invention has been developed to solve such problems. That is, to provide a secondary seal device for a low temperature tank top pipe that can securely seal the top pipe of the low temperature tank, and to safely and promptly replace the valve, and a valve replacement method using the device. is there.
[0007]
[Means for Solving the Problems]
According to the present invention, a balloon made of a flexible member connected to an air supply tube is inserted into the top pipe of a low-temperature tank storing liquefied gas, and air is supplied from the air supply tube to inflate the balloon. In the case of replacing the valve provided at the top of the top pipe after sealing the top pipe, the secondary seal device for sealing the top pipe from the further outside of the balloon, the secondary seal device, A low-temperature tank top pipe comprising: a pair of flexible members that are combined to form a ring; and a compression mechanism that compresses the flexible members in the axial direction of the top pipe and presses them against the inner wall of the top pipe. A secondary sealing device is provided.
[0008]
According to a preferred embodiment of the present invention, the flexible member is divided in the radial direction of the top pipe. In addition, the compression mechanism is combined with a hollow shaft that is in close contact with the air supply tube, a lower plate that is fixed to the hollow shaft and supports the lower surface of the flexible member, and an upper surface of the flexible member And an adjustment mechanism for adjusting the distance between the lower plate and the upper plate, and a rubber packing fixed along the inner surface of the hollow shaft.
[0009]
Furthermore, according to a preferred embodiment of the present invention, the adjusting mechanism includes a nut fixed to the upper surface of the lower plate, and a stud bolt screwed into the nut through a through hole provided in the upper plate. And a wing nut screwed onto the stud bolt from the upper surface side of the upper plate.
[0010]
According to a preferred embodiment of the present invention, the pair of ribs are fixed to the hollow shaft so as to be flush with the cut surface of the secondary sealing device, and the ribs are provided with through holes. The secondary seal device is fixed to the air supply tube by tightening a bolt through the through hole to be tightened with a nut.
[0011]
Further, according to the present invention, the first step of fixing the container having the lower end opened to the upper part of the existing valve provided in the top pipe of the low temperature tank for storing the liquefied gas and purging the inside with the inert gas, A second step of opening the existing valve and inserting a balloon made of a flexible member into the top pipe and inflating the balloon to seal the top pipe; a third step of removing the container and the existing valve; and a fourth step of placing the second sealing device for further sealing the top pipe on the outside of the balloon, and a fifth step of attaching the new valve at the top pipe, thereby releasing the secondary sealing device, the new valve A sixth step of fixing the container on the top of the container and purging the interior with an inert gas; and deflating the balloon, pulling out the balloon and the secondary seal device from the gap of the new valve, and closing the new valve A seventh step, an eighth step and, valve replacement method using the secondary seal device of the low temperature tank top pipe, characterized in that it consists of removing the last said container is provided.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described below with reference to FIGS. In addition, in each figure, the same code | symbol is attached | subjected to the part which is common in the past, and the overlapping description is abbreviate | omitted.
[0013]
1 and 2 are views showing a secondary sealing device for a low-temperature tank top pipe according to the present invention. FIG. 1 is a sectional view thereof, and FIG. 2 is a top view thereof.
[0014]
The secondary sealing device 6 shown in these drawings includes a pair of flexible members 7 and 7 (for example, natural rubber and Teflon are used) that are combined to form a ring, and the flexible member 7. The compression mechanism 8 for compressing in the axial direction of the top pipe 2 and pressing it against the inner wall of the top pipe 2.
[0015]
The compression mechanism 8 is combined with the hollow shaft 9 that is in close contact with the air supply tube 3 that supplies air from the air supply device 26 to the sealing balloon 4, and is fixed to the hollow shaft 9 and is flexible. The lower plate 10 that supports the lower surface of the member 7, the upper plate 11 that supports the upper surface of the flexible member 7, the adjustment mechanism 12 that adjusts the distance between the lower plate 10 and the upper plate 11, and the hollow shaft 9 The rubber packing 13 is fixed along the inner surface.
[0016]
Further, the adjusting mechanism 12 includes a nut 14 fixed to the upper surface of the lower plate 10, a stud bolt 16 screwed into the nut 14 through a through hole 15 provided in the upper plate 11, and the stud bolt 16. The wing nut 17 is screwed into the upper plate 11 from the upper surface side. Two are provided in parallel with the cut surface 18 of the secondary seal device 6 with the hollow shaft 9 interposed therebetween, and another one is provided at a position of 90 ° with them (that is, the secondary seal device 6). A total of six adjustment mechanisms 12 are provided.) Of course, this number may be increased or decreased depending on conditions such as the material of the flexible member 7 and the weight of the secondary seal device 6.
[0017]
If the secondary sealing device 6 is configured in this way, the operation shown in FIG. 3 is achieved. First, as shown in FIG. 3 (A), the secondary seal device 6 is combined so as to be closely overlapped and fitted into the air supply tube 3, and the wing nut 17 is tightened while maintaining this state. ), The flexible member 7 is compressed and projects in the radial direction of the top pipe 2. When the wing nut 17 is further tightened, the flexible member 7 is pressed against the inner wall of the top pipe 2 as shown in FIG. 3C, and the hollow shaft 9 is pressed against the air supply tube 3 by its elastic force. . When further tightened, the secondary sealing device 6 can be firmly fixed to the air supply tube 3 and the top pipe 2 can be sealed. In addition, since the rubber packing 13 is provided in the contact surface of the air supply tube 3 and the hollow shaft 9, it is also in the state sealed firmly here.
[0018]
4 and 5 show the secondary sealing device shown in FIGS. 1 and 2 provided with fixing means, FIG. 4 is a sectional view thereof, and FIG. 2 is a top view thereof.
[0019]
In the present embodiment, as shown in FIG. 5, a pair of ribs 19 and 19 are fixed to the hollow shaft 9 and the lower plate 10 so as to be flush with the cut surface 18 of the secondary seal device 6, and these ribs A through-hole (not shown) is provided in 19, and the secondary seal device 6 is tightened with a nut 21 through a bolt 20 in a through-hole (not shown) facing when the secondary seal device 6 is combined. This is fixed to the air supply tube 3. Further, as shown in FIG. 5, if the flexible member 7 is divided into an upper flexible member 7a and a lower flexible member 7b in the vertical direction, the adjusting mechanism 8 is operated to operate the upper flexible member. A gap is provided between the member 7a and the lower flexible member 7b, or the upper flexible member 7a is removed, and the bolt 20 and the nut 21 are tightened to connect the secondary seal device 6 to the air supply tube. 3 can be fixed.
[0020]
If the fixing means is provided in this way, even if a large pressure is generated in the secondary sealing device 6 for some reason, the root portion of the secondary sealing device 6 is firmly fixed, so the secondary sealing device. 6 will not come off. Further, even if the flexible member 7 is divided, it is sufficiently compressed by the compression mechanism 12 and thus has no effect on the sealing performance. The rib 19 may be provided on the upper part or the middle part of the hollow shaft 9.
[0021]
Next, with respect to the case where the butterfly valve which is an existing valve is replaced with a gate valve which is a new valve by using the above-described secondary sealing device of the present invention, FIGS. 6 to 9, FIGS. 11 to 13 and FIG. The description will be given with reference. Since the first to third steps and the eighth step of the present invention described below are the same as the first to third steps and the sixth step of the conventional valve replacement method, the description thereof will be simplified. .
[0022]
(1) In FIG. 11, the air lock chamber 22 is fixed to the upper part of the butterfly valve 5 provided in the top pipe 2 of the low temperature tank 1 for storing the liquefied gas, and the inside thereof is purged with nitrogen (first step).
(2) In FIG. 12, the butterfly valve 5 is opened and the sealing balloon 4 is inserted into the top pipe 2, and the balloon 4 is inflated to seal the top pipe 2 (second step).
(3) In FIG. 13, the air lock chamber 22 and the butterfly valve 5 are removed (third step).
(4) In FIG. 6, the secondary sealing device 6 described above is inserted into the top pipe 2, and the flexible member 7 is compressed by the compression mechanism 12 and pressed against the inner wall of the top pipe 2 (see FIG. 3). The outer side of 4 is sealed (fourth step).
(5) In FIG. 7, the gate valve 23 is attached to the top pipe 2 (fifth step). Here, the new valve is a gate valve, but any valve can be used as long as the secondary seal device 6 can pass through when the valve is opened. For example, there are other sluice valves.
(6) In FIG. 8, the compression mechanism 12 of the secondary seal device 6 is loosened to separate the flexible member 7 from the inner wall of the top pipe 2, and an air lock chamber 22 is fixed to the upper part of the gate valve 23 to Is purged with nitrogen (sixth step). At this time, the sealing balloon as the primary seal may be cracked or deflated. However, the compression mechanism 12 is loosened so that the air lock chamber 22 can be fixed immediately.
(7) In FIG. 9, the valve 27 is opened, the sealing balloon 4 is deflated, the sealing balloon 4 and the secondary sealing device 6 are extracted from the gap between the gate valves 23, and the gate valve 23 is closed (seventh step).
(8) Finally, in FIG. 16, the air lock chamber 22 is removed (eighth step).
[0023]
In addition, when replacing a valve such as a gate valve that can pass the secondary sealing device 6 when the valve is opened with a valve that can pass a similar secondary sealing device 6 in the second step, If the secondary sealing device 6 is inserted together with the balloon 4, the valve can be replaced in substantially the same process as the conventional valve replacement method using only the sealed balloon 4.
[0024]
Thus, according to the valve replacement method using the secondary seal device 6 of the present invention, since the secondary seal device 4 is divided into two parts, it is possible to quickly remove and attach the seal balloon 4 and The top pipe 2 can be reliably sealed from the outside.
[0025]
In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0026]
【The invention's effect】
As described above, according to the secondary sealing device for the low-temperature tank top pipe and the valve replacement method using the device, even if the sealing balloon as the primary seal is broken or deflated, the outer side is further sealed 2 Since the next sealing device is installed, liquefied gas does not spout outside. Further, since the secondary seal device is divided into two parts so that the attachment / detachment can be performed quickly, the valve can be replaced quickly. Therefore, it has an excellent effect that the top piping of the low-temperature tank is securely sealed, and the valve replacement can be processed safely and quickly.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a secondary seal device for a low-temperature tank top pipe according to the present invention.
FIG. 2 is a top view showing a secondary sealing device for a low-temperature tank top pipe according to the present invention.
FIG. 3 is a view showing the operation of the secondary sealing device of the present invention.
4 is a cross-sectional view of the secondary sealing device shown in FIG. 1 provided with fixing means.
5 is a top view of the secondary sealing device shown in FIG. 1 provided with fixing means. FIG.
FIG. 6 is a diagram showing a fourth step of the valve replacement method using the secondary seal device of the present invention.
FIG. 7 is a view showing a fifth step of the valve replacement method using the secondary seal device of the present invention.
FIG. 8 is a diagram showing a sixth step of the valve replacement method using the secondary seal device of the present invention.
FIG. 9 is a diagram showing a seventh step of the valve replacement method using the secondary seal device of the present invention.
FIG. 10 is an external view of a top pipe of a low-temperature tank.
FIG. 11 is a diagram showing a first step of a conventional valve replacement method and a first step of the valve replacement method of the present invention.
FIG. 12 is a diagram showing a second step of the conventional valve replacement method and a second step of the valve replacement method of the present invention.
FIG. 13 is a diagram showing a third step of the conventional valve replacement method and a third step of the valve replacement method of the present invention.
FIG. 14 is a diagram showing a fourth step of the conventional valve replacement method.
FIG. 15 is a diagram showing a fifth step of the conventional valve replacement method.
FIG. 16 is a diagram showing a sixth step of the conventional valve replacement method and an eighth step of the valve replacement method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Low temperature tank 2 Top piping 3 Air supply tube 4 Balloon which consists of flexible members (seal balloon)
5 Existing valve (butterfly valve)
6 Secondary sealing device 7 Flexible member 8 Compression mechanism 9 Hollow shaft 10 Lower plate 11 Upper plate 12 Adjustment mechanism 13 Rubber packing 14, 21 Nut 15 Through hole 16 Stud bolt 17 Wing nut 18 Cutting surface 19 Rib 20 Bolt 22 Lower end Open container (air lock chamber)
23 New valve (gate valve)
24 Nozzle 25 Nitrogen supply device 26 Air supply device 27 Valve

Claims (6)

  Insert a balloon made of a flexible member connected to the air supply tube into the top pipe of the low temperature tank that stores the liquefied gas, and supply air from the air supply tube to inflate the balloon to seal the top pipe From the above, when replacing the valve provided in the upper part of the top pipe, a secondary seal device for sealing the top pipe from the outside of the balloon, the secondary seal devices are combined to form a ring. And a compression mechanism that compresses the flexible member in the axial direction of the top pipe and presses the flexible member against the inner wall of the top pipe.   The secondary sealing device for a cryogenic tank top pipe according to claim 1, wherein the flexible member is divided in a radial direction of the top pipe.   The compression mechanism is combined with a hollow shaft that is in close contact with the air supply tube, a lower plate that is fixed to the hollow shaft and supports the lower surface of the flexible member, and supports the upper surface of the flexible member. The top part of the low-temperature tank according to claim 1 or 2, comprising: an upper plate to be adjusted; an adjustment mechanism for adjusting a distance between the lower plate and the upper plate; and a rubber packing fixed along the inner surface of the hollow shaft. Secondary sealing device for piping.   The adjusting mechanism includes a nut fixed to the upper surface of the lower plate, a stud bolt screwed into the nut through a through hole provided in the upper plate, and screwed to the stud bolt from the upper surface side of the upper plate. The secondary sealing device for a low-temperature tank top pipe according to any one of claims 1 to 3, further comprising a wing nut.   A pair of ribs are fixed to the hollow shaft so as to be flush with the cut surface of the secondary sealing device, and the ribs are provided with through holes. The secondary sealing device for a low-temperature tank top pipe according to any one of claims 1 to 4, wherein the secondary sealing device is fixed to the air supply tube. A first step of fixing a container having an open lower end to an upper part of an existing valve provided in a top pipe of a low temperature tank for storing a liquefied gas, and purging the inside with an inert gas;
A second step of opening the existing valve and inserting a balloon made of a flexible member into the top pipe, inflating the balloon and sealing the top pipe;
A third step of removing the container and the existing valve;
A fourth step of installing the secondary sealing device according to claim 1 for further sealing the top pipe outside the balloon;
A fifth step of attaching a new valve to the top pipe;
A sixth step of releasing the secondary sealing device, fixing the container to the top of the new valve, and purging the interior with an inert gas;
A seventh step of deflating the balloon, extracting the balloon and the secondary seal device from the gap of the new valve, and closing the new valve;
Finally, an eighth step of removing the container,
A valve replacement method using a secondary seal device for a low-temperature tank top pipe, characterized by comprising:

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